The present invention relates to a sealing cover for landfill and, more particularly, to a plastic foam cover for landfill.
In the United States, municipal, state and/or federal regulations govern the operation of landfills which receive garbage deposits during the day. A common requirement for such regulations includes covering the day's deposit of garbage with a layer of compacted earth approximately six inches deep to prevent, among other things, the escape of odors and blowing paper, the proliferation of pests, such as flies, rodents and birds and the leaching of toxic or disagreeable components from the garbage.
This task of placing and compacting the earth cover represents a very significant fraction of the cost of operating a landfill employing, as it does, significant labor and heavy equipment.
Such compacted earth cover performs its principal function for only a day or so. That is, each day's layer of garbage is covered at the end of the day and further layer of garbage with compacted earth topping is deposited in the following day.
Besides the cost of applying the compacted earth cover, it is recognized that multiple layers of earth fill used in this way tend to consume a significant volume of landfill which might otherwise be used for receiving garbage. As is well known, many areas are rapidly using up their available landfill acreage and any reduction in use rate of the landfill volume is desirable.
Various types of plastic foam have been in use for such applications as building insulation, etc. Common types of plastic foam include, for example, foam made by the Isoschaum process described in U.S. Pat. No. 2,860,856 wherein a foaming mixture of a foaming agent solution and air is formed and this mixture is then, in turn, mixed with a liquid synthetic resin such as precondensate of urea and formaldehyde. The resulting foam is then cured by a curing accelerator for the resin such as, for example, oxalic or other acid, which is added to the foam just before it is expelled from the apparatus so that the foam tends to cure and harden very soon after it is deposited.
Typically an air pressure of between about 55 and about 85 pounds per square inch is employed both for the formation of foam bubbles and also for urging the foam and hardening agent from the apparatus. The applicant has discovered that the prior art apparatus is capable of applying a layer of foam having a minimum thickness of about two inches on a substrate. When thus applied, such a layer of foam is capable of preventing the escape of gases and loose paper as well as performing the other desirable functions of a compacted layer of topsoil. However, a two-inch layer of a typical foam which is delivered at a rate of about two to two and a half cubic feet per minute, although effective, does not have the type of economic advantage over compacted topsoil that the applicant wishes to obtain. In addition, foam produced in the manner of the prior art hereinabove described tends to fora a layer upon the substrate garbage rather than penetrating into and filling crevices, etc. Thus, little or no mechanical keying of the foam layer into an uneven substrate is obtained. Thus, separation of the foam layer from the substrate is possible, and the foam layer tends to bridge air spaces below it thus tending to reduce the weight-bearing capability of the layer.
In addition to the preceding, a maximum delivery rate of two to two and a half cubic feet per minute limits the application rate of a two-inch layer of foam by one person to about 12 or 15 square feet per minute. Thus to cover a typical landfill area of 4,000 feet would take between 4.5 and 5.5 hours for one man.